Unnamed (west of Crab Bay)

Occurrences, Undetermined

Alternative names

Tyee?

Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Zn
Other commodities Barite
Ore minerals barite; chalcopyrite; galena; malachite; pyrite; sphalerite; tetrahedrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-5
Latitude 55.111
Longitude -131.397
Nearby scientific data Find additional scientific data near this location
Location and accuracy
This site includes a roughly 0.3-mile-long line of occurrences and a prospect pit, at elevations of about 200 to 300 feet, midway between the outlet of 'Sink Lake' and the head of Crab Bay. The pit and occurrences are in section 16, T. 78 S., R. 93 E., of the Copper River Meridian, and the map coordinates are for the approximate center of the line. The site corresponds to loc. 5 in Berg (1972 [I 684]), loc. 146 in Elliott and others (1978), and loc. 33a-c in Karl (1992). The location is accurate within 0.1 mile.
Also see Additional comments.

Geologic setting

Geologic description

The country rocks in the area of this site are recrystallized rhyolite and overlying, locally dolomitic, limestone (Berg, 1972). These Upper Triassic rocks are complexly folded and faulted, and were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time.
The occurrences consist of quartz pods and fissure veins up to about a foot thick in carbonate and volcanic rocks, and of quartz-calcite-barite veins in locally silicified carbonate rock (Karl, 1992, loc. 33). In addition to barite, these veins contain white mica, pyrite, sphalerite, and galena.
At and near a prospect pit, samples of brecciated, dolomitic limestone carrying stringers and disseminated grains of pyrite, galena, and chalcopyrite; of nearby sulfide quartz veins; and of sheared pyritic rhyolite at the limestone contact contained as much as 0.05 ppm Au, 70 ppm Ag, 1000 ppm Pb, more than 1% Zn, 20 ppm Mo, and more than 5000 ppm Ba (Berg, 1972, loc. 5; Karl, 1992, loc. 33c).
Reports based on fieldwork by private interests in the 1970s describe a mineralized zone 150 feet wide and 450 feet long at a rhyolite-dolomite contact. The zone contains quartz veins carrying galena, sphalerite, tetrahedrite?, and malachite (Karl, 1992, loc. 33). Another 150-foot by 450-foot zone in dolomite locally contains disseminated sulfides that assay up to 8% lead and zinc, as well as quartz veins containing sphalerite and galena. Two soil samples in rhyolite near the dolomite contained detectable gold; and pyritic limestone contained 150 ppm Pb.
Geologic map unit (-131.398680202847, 55.1106597252423)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization The fissure veins probably are Late Cretaceous or younger in age.
Alteration of deposit Local silicification, sericitization, and dolomitization; minor oxidation of copper minerals.

Production and reserves

Workings or exploration
Prospect pit, probably dating to the 1930s. Samples at and near this pit contained as much as 0.05 ppm Au, 70 ppm Ag, 1000 ppm Pb, more than 1% Zn, 20 ppm Mo, and more than 5000 ppm Ba (Berg, 1972, loc. 5; Karl, 1992, loc. 33c).
Reports based on fieldwork by private interests in the 1970s describe a mineralized zone 150 feet wide and 450 feet long at a rhyolite-dolomite contact. The zone contains quartz veins carrying galena, sphalerite, tetrahedrite?, and malachite (Karl, 1992, loc. 33). Another 150-foot by 450-foot zone in dolomite locally contains disseminated sulfides that assay up to 8% lead and zinc, as well as quartz veins containing sphalerite and galena. Two soil samples in rhyolite near the dolomite contained detectable gold; and pyritic limestone contained 150 ppm Pb.
Indication of production None

Additional comments

Early references to the Tyee prospect on Annette Island may refer to this site (Cobb and Elliott, 1980, p. 30).

References